package JZOffer;

import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
 
public class BinaryTree {
 
    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用
 
        public TreeNode(char val) {
            this.val = val;
        }
    }
 
 
    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
 
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
 
        return A;
    }
 
    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
 
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }
 
    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
 
        inOrder(root.left);
        System.out.print(root.val +" ");
        inOrder(root.right);
 
    }
 
    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
 
        postOrder(root.left);
        preOrder(root.right);
        System.out.print(root.val + " ");
    }
 
    /**
     * 获取树中节点的个数：遍历思路
     */
    public static int nodeSize = 0;
    int size(TreeNode root) {
        if (root == null) {
            return 0;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
        return nodeSize;
    }
 
    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
 
    int size2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return size2(root.left) + size2(root.right)+1;
    }
 
 
    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;
 
    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
 
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }
 
    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
 
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }
 
    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null || k<=0) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left, k-1) + getKLevelNodeCount(root.right, k-1);
    }
 
    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);
        return leftHeight > rightHeight ? leftHeight+1 : rightHeight+1;
    }
 
 
    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode ret1 = find(root.left, val);
        if (ret1 != null) {
            return ret1;
        }
        TreeNode ret2 = find(root.right, val);
        if (ret2 != null) {
            return ret2;
        }
        return null;
    }
 
    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        Queue<TreeNode> qu = new LinkedList<>();
        qu.offer(root);
        while (!qu.isEmpty()) {
            TreeNode cur = qu.poll();
            System.out.print(cur.val + " ");
            if (cur.left != null) {
                qu.offer(cur.left);
            }
            if (cur.right != null) {
                qu.offer(cur.right);
            }
        }
    }
 
 
    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
      if (root == null) {
          return true;
      }
      Queue<TreeNode> queue = new LinkedList<>();
      queue.offer(root);
      while (!queue.isEmpty()) {
          TreeNode cur = queue.poll();
          if (cur != null) {
              queue.offer(cur.left);
              queue.offer(cur.right);
          } else {
              break;
          }
      }
      // 这时判断队列里面的元素是不是全是空元素
      while (!queue.isEmpty()) {
          TreeNode cur = queue.poll();
          if (cur != null) {
              return false;
          }
      }
      return true;
    }
}